exofs: don't leak io_state and pages on read error

Same bug as fixed by Idan for write_exec was in read_exec.
Fix the io_state leak and pages state on read error.

Also while at it:
The if (!pcol->read_4_write) at the error path is redundant
because all goto err; are after the if (pcol->read_4_write)
bale out.
Signed-off-by: NBoaz Harrosh <bharrosh@panasas.com>

fs/exofs/inode.c

@@ -361,12 +361,12 @@ static int read_exec(struct page_collect *pcol)
 	return 0;
 
 err:
-	if (!pcol->read_4_write)
-		_unlock_pcol_pages(pcol, ret, READ);
-
-	pcol_free(pcol);
-
+	if (!pcol_copy) /* Failed before ownership transfer */
+		pcol_copy = pcol;
+	_unlock_pcol_pages(pcol_copy, ret, READ);
+	pcol_free(pcol_copy);
 	kfree(pcol_copy);
+
 	return ret;
 }